Tuning system of antenne



July 29, 1924. 1502.848

F. CONRAD TUNING SYSTEM OF ANTENNAE Filed July '7 1920 BIL. T /2 5' WITNESSES: ENVENTOR ya a gan/f Con/"ad Patented July 29, 1924.

UNITED STATES,

PATENT OFFICE .rmx comma, or PITTSBURGH, rnunsnvnnm, nssrcnoa ro WESTINGHoUSE nnnc'rnxc & MANUFACTURING comm, A. conroan'rron orrmsynvmm TUNING sxs'rnu or Aurnmm.

Application filed m 7, 1 20. Serial no.1 394,520.

To all whom it may concern: 7

Be it known that I, FRANK CONRAD, a citizen of the United States, and a resident of Pittsburgh, in the county of Allegheny a and State of Pennsylvania, have invented a new and useful Improvement in Tuni Systems of Antennae, of which the following is a specification.

ThlS invention relates to wireless tele- 10 graphic systems and-particularly tosuch'systerns as, have capacitance and self-inductance in their grounded, antenna circuits.

Heretofore, a great selectivity of signals has been considered well-nigh impossible of attainment, particularly in the use of undamped waves. I have discovered that, by a suitable introduction of reactances into the antenna circuit, I am able to obtain .a'degree of responsiveness to particular wave lengths, whether. for damped or undamped systems, which is very much greater than has heretofore been secured.

An important feature of'my invention,

ducing suitable reactances in order that such high degree ofresponsiveness may be secured, Without affecting the wave length to any material de ee.

A further object of my invention is to so automatically correlate the simultaneous variations in the series self-induction and the capacity that a minimum amount of manipulation will be necessary for attaining maximum responsiveness'without sub stantially affecting the wave length. i

A still further object of the invention is the simplification in the construction of the receiving circuits for damped waves, which therefore, is the method ormeans of introproper inspection of the drawings when taken in conjunction with the accompanymg description.

Fig. 1 is a diagrammatic view of a simplifi ed form of my invention; Fig. 2 is a view similar to Fig. 1, except that inductive coupling is employed; Fig. 3 is a diagrammatic view of a preferred embodiment of my invention arranged for a triode circuit.

It has been usual hitherto, in order to secure maximum responsiveness, to tune the antenna circuit for a given wave length by means of a loading reactance. I have found, however, that'the degree of responsiveness, both in sharpness and loudness, may be secured by introducing, in series with such resonant antenna system, a device which may be referred to as a selective responder, such selective responder comprising a capacitance 1 and inductances 2, 3 intercalated into the antenna circuit I 4, 5. The selective responder 1, 2, 3 comprises also a member 6 which causes the capacitance 1 to automatically vary in proper correspondence to the variable-inductance member 3. The series inductance 2 is also adjustable, but independently of the inductance 3.

In the preferred embodiment of my invention, the adjustments of capacitance 1, relative'to the adjustment of inductance 3 by means of the operatin member 6 are so arranged. that .the wave ength of the antenna system 4, 2, 3, 5 of Fi 1, for example, shall remain 'substantia ly constant.

From this point of view, it will be seen that the inductance 2 acts substantially as a loading coil in order to tune the antenna system to the proper wave length. In order, therefore, to obtain a maximum ofotential across the detector element 7, provide a lead 8 connecting the detector to the junction 9 ofthe inductance 2 with the capacitance 1. A further lead 10 connects the detector 7 through a telephone receiver 11, to the junction 12 of the variable inductance 3 with the base 5 of the antenna system.

' In this manner, it is seen that, whereas the potential across the detector was formerly due to the potential across the loading coil member 2, in the method of it my invention I obtain an increased potential for the detector circuit by virtue of the leads 8 and 10 connecting across the two series reactanoes 2 and 3.

As a consequence of my invention, I find that a greater selectivity, as well as magnitude of response, is obtained by having the two balancing reactances 2 and 3 inserted into the antennacircuit. It will be found, however, that there is one particular setting of the operating member 6 which gives maximum selective response to any incoming signal, whether of the damped or the undamped variety. By the above method of adjustment, therefore, I not only achieve the usual responsiveness due to resonance but I also obtain an increased and much sharpor response by means of my selective respender.

The system of circuits in Fig. 2 is sub stantially equivalent to that shown in Fig. 1. However, in Fig. 1 the coupling is shown conductive while the coupling in Fig. 2 is, alternatively, inductive.

In Fig. 3, I make use of the iegenerative principle by connecting the plate 13 of a triode 14 to the secondary coupling member 2' associated with the primary coupling member or inductance 2.- secondary coupling member 3 is associated with a primary coupling member or inductance 3. The two inductances 2', 3 are then connected, through the telephone re ceiver 11, to a battery 15 and filament 16 of the triode. On the other hand, the grid 17 is connected to the junction 9 of the antenna circuit proper, whereas the filament 16 is also connected to the junction 12 between the primary inductance 3 and the antenna base 5.

Preferably, I arrange a condenser 18, with a grid leak 19, in the lead 8 joining the grid 17 of Fig. 3 to the antenna. shunting condenser 20 is provided for the telephone-receiver circuit, as is usual in vacuum-tube operation.

In general, I provide switches 21 and 22 for the capacitance and related inductances 3 in the antenna circuit. Similarly, in Fig. 3, I provide" also an additional switch 22 to short circuit the coupling coil 3' when necessary. The function of the above switches will appear from the following description of operation.

In order to tune for resonance in accordance with well established principles, I provide the loading coil 2 with an adjustable connection 23 in order to cut out more or less of the turns of the loading coil. How- 7 ever, to do this with any degree of ease n will require that the-switches 21 and 22 be closed, short-circuiting thereby the active elements of the selective responder.

After proper resonance has been secured with regard to the wave length, the switches 21 and 22 of Fig. 1 are then opened in order to increase the coupling of the detector cir- Similarly, themosses cuit and to cause the antenna circuit to have a relatively large inductance, thereby obtaining a low decrement and a consequent sharp tuning. The operating member 6 is then adjusted to secure the maximum degree of sharpness and loudness in the telephone receiver.

Where inductive coupling is employed, as in Figs. 2 and 3, it will be preferable to close the switch 22 at the same time the primary switches 21 and 22 are closed.

It will be apparent that, when the turns of the coupling coil 2 are entirely out out by means of the adjustable connection 23, for given wave -lengths, the selective responder may be used, both for obtaining resonance with respect to a particular wave length and maximum selective response in addition.

The invention, therefore, includes broad ly not only the addition of a primary coupling coil 2 but also the provision of an induction-coil member 3, which acts both as u loading coil and as an element of the selective responder. It may be observed that, for-certain amateur purposes, the latter may prove a preferable arrangement.

Having disclosed the nature of my invention, what I claim is:

1. An improved method in the art of signalling comprising the step of first adjusting a circuit for resonance to a given frequency and thereafter additively ad usting said circuit for maximum selective response While maintaining said resonant condition substantially undisturbed.

2. The combination With an electrical circuit including a variable inductor and a variable condenser, of common means for simultaneously varying said inductor and condenser in such manner that the algebraic sum of their reactances remains approximately constant.

3. A method of adjusting the responsiveness of a circuit having a given wave length comprising the steps of inserting a variable reactance into said circuit and compensating -for the resultant modified natural wave length by means of a variable reactance of different type.

{1. The combination with a tuned circuit, of common means for varying the inductance of the circuit and simultaneously and equally varying the capacitance.

5. A tuning system including a pair of reactors, each of said reactors having a relatively stationary element and a relatively movable element whereby the reactance between said elements may be varied by the adjustment of the relative positions thereof, and common means for simultaneously adjusting said reactors in such manner that the sum of the impedances of said reactors is substantially constant.

6. A radio receiving system including,

moaeae in combination, an antenna, a condenser serially connected thereto, a pair of serially connected inductors connected between said condenser and ground, a receiving circuit coupled to both of said inductors, means for inserting and removing said condenser and one of said inductors from said antenna circuit, and means for simultaneously varying said inductor and condenser in such manner that the algebraic sum of their reactances remains approximately constant.

7 The method of adjusting the constants of a radio receiving system including an an- 8. In combination with an antenna comprising a variable capacitance, a variable inductance mechanically coupled thereto and in series therewith and with said antenna, a ground connection for said variable inductance, and a further inductance also in series with said antenna.

9. In combination with an antenna comprising a variable capacitance and a variable inductance in series with each other and with said antenna, a ground connection for said variable inductance, a further inductance also in series with said antenna, and common means for operatively associating said variable capacitance and said first-mentioned variable inductance,whereby the algebraic sum of their reactances remains substantially constant.

10. In combination with an antenna having a capacitance 'in series, a primary coupling coil for said antenna, a secondary coupling, a triode bulb, and means associated with said triode bulb and said coupling coils for making a regenerative cou ling of said primary and secondary coupling coils, in further combination with means for o eratively associating said capacitance an primary coupling coil, whereby-the decrement of said antenna, capacitance and primary coil may be varied independent of the tuning thereof.

11. The combination with a grounded, tuned antenna-circuit having a point of substantially maximum potential near the ground, of means in series with said circuit for increasing said potential whilemaintaining the tuned wave-length substantially constant.

12. The combination with an antenna-circuit tuned to a given wave-length, of voltage-amplifying means for said wave-length in series with said circuit, means for compensating the efi'ect of said voltage-amplifying means on the tunin of-said circuit, and means for var ing sai voltage-amplifying means and sai compensating means in such manner as to maintain the tuning substantially constant.

13. A method of amplifying the signal due to an incoming wave comprising the step of tuning for a given wave length with minimum lumped inductance in the receiving circuit and, as a further step, balancing an introduced added inductance in said circuit by means of a compensating capacitance.

14. In combination, means for broadly tuning a circuit to resonance for a given wave length, additional means included in said circuit for sharpening such tuning so as to increase the intensity of the signal thereby.

' In testimony whereof, I have hereunto subscribed my name this 1st day of July, 1920.

FRANK CONRAD. 

